楚河汉界
Chǔ​hé Hàn​jiè

chessboard midline

楚河汉界 (楚河漢界) Chǔ​hé Hàn​jiè
chessboard midline
The middle line separating the two halves on a Chinese chessboard (Xiangqi).
dividing line
A line or boundary that separates two rival territories, factions, or opposing sides.
historical boundary
The literal river and border that divided the states of Chu and Han during their historical conflict.

Sources
Definitions
CC-CEDICT